Now let's do the experiment. It should be
done as close to noon as practical and on a
clear, cloudless day. Your instructor will supply
you with the items listed above. Measure 200
ml of cool water (close to ambient air temperature)
and pour it into the bottle. Then add a few
drops of India ink to the water until it is fairly
black.
Place the thermometer and cork in the bottle
and put the bottle in the shade close to where
you will do the experiment. This is to let the
water and thermometer come to ambient air
temperature. After several checks, a few minutes
apart, indicate that the temperature of the
water is neither rising nor falling (record this
temperature), you may prepare to place the
bottle in the direct sun.
The bottle should be propped so that its face
is as close to perpendicular to the sun's direction
as possible. You can assure this by noting
the shadow on a white card placed behind the
bottle. Until you are ready to start timing, have
a card or book or something opaque in front of
the bottle to block the direct rays from the sun.
(It will help to have a lab partner for this experiment.)
Remove the sun block and begin timing.
Allow the sun’s rays to strike the bottle for
about 20 minutes. This will be enough time to
cause the temperature of the water to rise several
degrees Celsius (See example.) Record the
temperature and elasped time.
Cool the water solution to ambient by placing
it under running water, and repeat the experiment.
Do the experiment three times total.